Based on the large percentage of cases with a confirmed family history of motor stereotypies, stereotypic movement disorder is thought to be moderately heritable. Children with stereotypies had significantly smaller putamen volumes, which suggests that the underlying anatomical site for complicated motor stereotypies may be premotor to posterior putamen circuits, unique cortical-striatal pathways linked to habitual behaviors. Stereotypic behavior is more likely to occur and people with lower cognitive functioning also respond less well to interventions. Individuals with moderate-to-severe/profound intellectual developmental disorder, who because of a specific syndrome, are more likely to exhibit stereotypical movements (like Rett syndrome) or environmental factors (such a setting with little to no stimulation, for example) tend to put people at a higher risk of stereotypies. Repeatedly harming oneself could be a behavioral trait. For example, in Lesch-Nyhan syndrome, there are both stereotypic dystonic movements and self-mutilation of fingers, lip biting, and other forms of self-injury unless the individual is restrained, and in Rett syndrome and Cornelia de Lange syndrome, self-injury may result from the hand-to-mouth stereotypies. Stereotypic behaviors may also result from a painful medical condition (e.g., middle ear infection, dental problems, gastroesophageal reflux).